Side sliding door lock remote doesn't work

My 2003 Sprinter cargo Side sliding door lock remote doesn't work. I have to manually lock and unlock it. All the other doors will iock and unlock with remote. I have to do the hit button once for 'lock-unlock' the press button again for the 'lock-unlock-lock' sequence so many other owners experience.
I have not found the culprit-cleaned all contacts, sprayed lithium lubricant on locking mechanisms. The blue and the green wires to the actuator solenoid show power when I hit the lock button on the remote. No power shown in any combination of the other three wires. No power at the contacts on the body for unlock when pressing remote unlock.
There is a ticking like a clock in the actuator when the side door is closed which corresponds to the red arrow flashing on the dash lock control buttons. It is a small voltage varying 0.45 to 1.26. Does anyone have an idea what is happening?
Is there a way to test the actuator solenoid, as they are expensive to replace if it is OK.
BTW this forum is incredible! Bought this Sprinter last May with 280K. Love it! Mel

While I guess you are onto the culprit with the clicking sound..........

Take a look at the parts catalog ... you may be able to use the rear door actuator's wiring to test the side door actuator. Forget the front doors for this as it takes too longer to remove the panels.

Does the door lock/unlock from the front counsel switch?

Does the door lock manually from the inside (I know you said it locks manually from the outside, but I have seen the internal push wire become disengaged)?

Remove it from the door a bit and see if it will work. Mine was out of alignment enough that the actuator had to work too hard, and it wouldn't lock. I bent some tangs, added a shim, or something and it was able to lock without resistance.

hkpierce, the side door will manually lock outside with the key and will lock manually from the inside. It will not lock or unlock with the dash switch or remote (fob). I read your helpful posts in my searches.
surlyoldbill, thank you. I have read many of your informative posts, not the problem here after I checked.
I have the front door panels off to check and lube those too. Had an issue with not being able to lock drivers door and the rear door-manually or by FOB. After scrubbing the door contacts and lubing door mechanisms, they are locking, unlocking.
So I'm wondering how to test the actuator.